Apparatuses and methods for identifying memory devices of a semiconductor device sharing an external resistance

ABSTRACT

Apparatuses and methods for identifying memory devices of a semiconductor device sharing an external resistance are disclosed. A memory device of a semiconductor device may be set in an identification mode and provide an identification request to other memory devices that are coupled to a common communication channel. The memory devices that are coupled to the common communication channel may share an external resistance, for example, for calibration of respective programmable termination components of the memory devices. The memory devices that receive the identification request set a respective identification flag which can be read to determine which memory devices share an external resistance with the memory device having the set identification mode.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the filing benefit of U.S. ProvisionalApplication No. 62/578,847, filed Oct. 30, 2017. This application isincorporated by reference herein in its entirety and for all purposes.

BACKGROUND

Semiconductor devices such as microcomputers, memories, gate arrays,among others, include input/output pins and an output circuit fortransmitting data to other devices, via a bus, transmission lines formedon a board, and the like. A circuit within the semiconductor device thatis responsible for transmitting data includes, for example, outputbuffers and drivers. For there to be optimum transmission, the impedanceof the transmitting device should be matched to the impedance of thetransmission network and receiving device.

As operational speeds of electronic devices increase, the swing oftransmitted signals decreases. However, as the signal swing width of atransmitted signal decreases, the negative effect of external noiseincreases. External noise can affect the reflection characteristics ofan output signal if there is an impedance mismatch at an interface.Impedance mismatches are caused by external noise or by noise on a powersupply voltage, temperature and process variations, among others. If animpedance mismatch arises, the transmission speed of the data decreases,and the data from a semiconductor device may become distorted. Thus, ina case where a semiconductor device receives distorted data, problemscan be caused by setup/hold failures or errors in reading received data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a system according to an embodiment of thedisclosure.

FIG. 2 is a block diagram of a semiconductor device according to anembodiment of the disclosure.

FIG. 3 is a block diagram of a memory device according to an embodimentof the disclosure.

FIG. 4 is a diagram of a mode register including various settings andflags related to impedance calibration and impedance settings accordingto an embodiment of the disclosure

FIG. 5 is a flow diagram for identifying (ZQ) groups of memory devicessharing an external resistance and the memory devices included in eachof the ZQ groups of a semiconductor device according to an embodiment ofthe disclosure.

FIG. 6 is a flow diagram of determining whether all of the ZQ groups ofa semiconductor device have been identified according to an embodimentof the disclosure.

FIG. 7 is a flow diagram of a ZQ ID mode operation for a memory deviceaccording to an embodiment of the disclosure.

FIG. 8 is a flow diagram of a ZQ ID request operation for a memorydevice according to an embodiment of the disclosure.

DETAILED DESCRIPTION

In order to mitigate these issues arising from an impedance mismatcharises, memory devices may include programmable termination componentsthat may be used to provide adjustable on-die termination and adjustableoutput driver impedance. The on-die termination may be adjusted toreduce impedance mismatch, for example, when signals (e.g., command,data, etc.) are provided to the memory devices. The programmabletermination components have impedance values that can be adjusted asoperating conditions change. In some implementations, programmabletermination components are calibrated to a known impedance which may bebased on voltage measurements made on a circuit node that couples to anexternal resistance.

Calibration of the programmable termination components typically occursin response to a memory command, which is provided to the memory device,for example, at power up, memory device reset, changing a frequency setpoint for memory device operation, or whenever initiating a calibrationprocess is desired. Following a time period after the initiation of thecalibration process, another memory command is provided to the memorydevice to apply the parameters determined during the calibration processto set the programmable termination components accordingly.

In some cases, a limited number of external connections are availablefor coupling to an external resistance. These external connections maybe shared between multiple devices that use the connection forcalibration purposes. However, it may not be apparent to devicesexternal to the memory, such as a system memory controller, which of themultiple devices of the memory share each of the external connections.As such, devices external to the memory may be unable to determine whichdevices in the memory to send commands for calibration operations. Toaddress this, and as described herein, a memory device of asemiconductor device may be set in an identification mode and provide anidentification request to other memory devices that are coupled to acommon communication channel.

FIG. 1 is a block diagram of a system 100 according to an embodiment ofthe disclosure. The system 100 includes a system memory controller 110and a system memory 120. The system memory controller 110 and the systemmemory 120 may communicate with each other over command-address bus 130and a data bus 140. The system memory controller 110 may control thesystem memory 120 by issuing commands and memory addresses associatedwith the commands over the command-address bus 130, for example, tostore data and to provide data. Data may be stored by the system memorycontroller 110 by issuing a write command to the system memory 120 andproviding write data on the data bus 140 to the system memory 120 to bestored. Data may be provided to the system memory controller 110 byissuing a read command to the system memory 120, which provides therequested read data on the data bus 140 to the system memory controller110.

The system memory 120 may include multiple semiconductor devices thatmay be accessed to store data and provide data when requested. Thesystem memory controller 110 may include multiple memory controllers,each communicating with and having access to a respective portion of thesystem memory 120. The system memory controller may further includememory device information storage for storing information related tomemory devices of the semiconductor devices of the system memory 120.

FIG. 2 is a block diagram of a semiconductor device 200 according to anembodiment of the disclosure. The semiconductor device 200 may be avolatile memory such as a SRAM or DRAM, or a non-volatile memory such asa FLASH memory or a ferroelectric memory. In one embodiment, the DoubleData Rate (DDR) memory, such as a Low Power Double Data Rate 5 (LPDDR5)memory. The semiconductor 200 may be included in the system memory 120of FIG. 1 in some embodiments of the disclosure.

The semiconductor device 200 includes a plurality of individual memorydevices 204 that may be arranged on one or more different semiconductordies, and further includes a package that contains and interconnects thevarious individual memory devices 204. The package may provide aplurality of external pins that couple to contact pads arranged on theinterior of the package. The pins and pads may provide electricalconnections such as between the memory devices 204 and the larger systemto which the semiconductor device 200 is coupled. The semiconductordevice 200 may include memory buses through which the larger systemcommunicates with the memory devices 204. For example, the semiconductordevice 200 may be associated with one or more memory controllers thatare configured to communicate commands, addresses, and data with thesemiconductor device 200 over the memory buses. Each memory controllermay communicate across a respective memory bus that couples the memorycontroller to one or more individual memory devices 204 of thesemiconductor device 200. For example, as shown in FIG. 2, a memorycontroller MC0 may communicate with a first group of memory devices 204and a memory controller MC1 may communicate with a second group ofmemory devices 204 across respective memory busses. The memorycontrollers MC0 and MC1 may be included in a system memory controller(e.g., system memory controller 110 of FIG. 1) in some embodiments ofthe disclosure. The memory controllers MC0 and MC1 may be included inseparate system memory controllers, or not included in a memorycontroller, in other embodiments of the disclosure.

Each memory bus may include a command-address bus 208 that providescommands and addresses to the semiconductor device 200 and may furtherinclude a data bus 210 over which data is provided. Each memory bus mayadditionally include chip select lines (not shown) that may beselectively asserted to enable one of the memory devices 204 to send orreceive data across the common memory bus. The memory devices 204 may beconfigured in multiple different ways and the chip select linesconfigured accordingly to control selection of the memory devices 204.For example, in some embodiments of the disclosure, a two or more memorydevices 204 are coupled to a common chip select line, whereas in otherembodiments of the disclosure, each memory device 204 is coupled to arespective chip select lines. Some embodiments of the disclosure mayinclude memory devices 204 that have respective chip select lines incombination with other memory devices 204 that have a common chip selectline. Through the combination of individual chip select lines and commonaddress, data, and control lines, the larger system may communicate andcontrol the semiconductor device 200.

The semiconductor device 200 may also include first and second internalterminals, which may be referred to as ZQ terminals 222 and 224. A firstexternal resistance RZQ0 may couple to the ZQ terminal 222 and a secondexternal resistance RZQ1 may couple to the ZQ terminal 224. The memorydevices 204 coupled to the ZQ terminal 222 to share the first externalresistance RZQ0 for impedance calibration represent a first (ZQ) group232. The memory devices 204 coupled to the ZQ terminal 224 to share thesecond external resistance RZQ1 for impedance calibration represent asecond (ZQ) group 234. The memory devices 204 of the first ZQ groupshare a single ZQ resource (i.e., external resistance RZQ0) and thememory devices of the second ZQ group share a single ZQ resource (i.e.,external resistance RZQ1). The memory devices 204 of the first ZQ group232 are coupled to a communication channel 242 through which the memorydevices 204 communicate with each other. Similarly, the memory devices204 of the second ZQ group 234 are coupled to a communication channel244 through which the memory devices 204 communicate with each other.For example, information or a request provided by one of the memorydevices 204 of a ZQ group is received by the other memory devices 204 ofthe same ZQ group.

Due to multiple memory devices 204 of a memory group sharing oneexternal resistance RZQ, contention may occur in the event that thefirst and second memory both devices 104 perform respective calibrationoperations concurrently. As a result, the memory devices 204 may need toarbitrate for use of the external resistance RZQ during calibrationoperations. For example, the semiconductor devices 204 of the first ZQgroup 232 may need to arbitrate for use of the external resistance RZQ0during calibration operations and obtain control over the externalresistance RZQ0 before initiating calibration operations. Likewise, thesemiconductor devices 204 of the second ZQ group 234 may need toarbitrate for use of the external resistance RZQ1 during calibrationsoperations and obtain control over the external resistance RZQ1 beforeinitiating calibration operations.

FIG. 2 shows two ZQ groups as included in the semiconductor device 200.In other embodiments of the disclosure, a semiconductor device mayinclude fewer or greater ZQ groups. Additionally, in some embodiments ofthe disclosure, each of the ZQ groups of the semiconductor device mayinclude the same number of memory devices, whereas in other embodimentsof the disclosure, two or more the ZQ groups may have different numbersof memory devices.

FIG. 3 is a block diagram of a memory device 300 according to anembodiment of the disclosure. In some embodiments of the disclosure, thememory device 300 may be included in the semiconductor device 200 as thememory devices 204.

The memory device 300 includes a command decoder 310 that receives andprocesses commands from a memory bus. The command decoder 310 may beconfigured to recognize a plurality of commands that correspond tovarious operations that may be executed by the memory device 300. Forexample, the command decoder 310 may receive and decode a read or writecommand. A read or write command generally directs the memory device 300to read or write data to or from one or more memory cells in a memoryarray 314. In performing a corresponding read or write operation, thecommand decoder 310 may provide internal control signals to read datafrom and write data to the memory array 314. Row and column addresssignals may be provided to an address latch in the memory device 300through an address bus. The address latch may then provide a separatecolumn address and a separate row address. The address latch may providerow and column addresses to a row address decoder 318 and a columnaddress decoder 322, respectively. The row address decoder 318 mayinclude signal line drivers that activate respective rows of memorycells in the array 314 corresponding to received row addresses. Thecolumn address decoder 322 may select signal lines extending through thearray 314 corresponding to respective column addresses. The selectedsignal line or lines corresponding to a received column address may becoupled to read/write circuitry to provide read data to an output databuffer 326 via an input-output data path 330. Write data may be providedto the memory array 314 through an input data buffer 334 and the memoryarray read/write circuitry. A clock generator (not shown) may provide aninternal clock signal responsive to an input clock signal. The internalclock signal may be used by circuits of the memory, for example, theoutput data buffer 326 and the input data buffer 334.

Calibration operations may be initiated by command, for example, from asystem memory controller. Calibration operations may be initiatedautomatically, for example, as part of a power-on sequence that occurswhen power is first provided to the memory device 300, and/or when thereis a change in operating condition for the memory device 300.

A calibration command is generally issued to cause a memory device 300to calibrate an impedance of each of programmable termination component338, sometimes referred to as On Die Termination (ODT) and the outputbuffer 326. As known, an ODT circuit may be adjusted to provide amatched impedance. In FIG. 3, the programmable termination component 338is depicted independently of the output buffer 326. However, it is alsopossible that the output buffer includes the programmable terminationcomponent 338 as a part of the output buffer. In this case, the ODToperation is performed by at least a part of the output buffer 326. Uponreceipt, the command decoder 310 decodes the calibration command andprovides control signals to an impedance controller 340, which generallyoperates to adjust impedances of the programmable termination component338 and the output buffer 326. Each of the programmable terminationcomponent 338 and the output buffer 326 generally includes a group ofpull-up and pull-down transistors that, are controlled to be enabled ordisabled by the impedance controller 340. The impedance controller 340enables/disables the pull-up and pull-down transistors on or off so thatthe impedance of the output buffer 326 matches the impedance of the databus. In this way, signal reflections that result from impedancemismatches are avoided.

The impedance controller 340 may be coupled to an external resistanceRZQ that is used for calibration of the impedances of the programmabletermination component 338. The impedance controller 340 is also coupledto a communication channel. As previously described, memory devices of aZQ group may be coupled to a communication channel to communicate witheach other, for example, providing and receiving information and/orrequest. The impedance controller 340 includes a calibration circuit 342and an arbitration circuit 346.

The calibration circuit 342 generally operates by measuring the voltageat a ZQ terminal and using that voltage to adjust the impedance of theprogrammable termination component 338 and the output buffer 326. Whencurrent is provided from the external resistance RZQ as part of acalibration operation, the current may be received by the calibrationcircuit 342. The impedance of the external resistance RZQ may representthe impedance that each of the programmable termination component 338and the output buffer 326 provides to the data bus to which it iscoupled. The impedance of each of the programmable termination component338 and the output buffer 326 may vary as various operating conditionschange. For example, temperature changes that occur during the operationof the memory device 300 may lead to variations in these impedances.

By measuring the impedance of the external resistance RZQ, of whichimpedance is basically stable regardless of changes in conditions, thecalibration circuit 342 makes an impedance measurement that correspondsto current operating conditions. This impedance measurement may then beused to set the impedance value of each of the programmable terminationcomponent 338 and the output buffer 326 such that it matches currentoperating conditions. For example, the calibration circuit 342 maymeasure the voltage at the ZQ terminal and compare that voltage to aninternal reference voltage. This comparison may be made through theoperation of a comparator that outputs a comparison result. Thecomparison result may then be used to step up or step down the voltageat the ZQ terminal so as to bring the voltage of the ZQ pin closer tothe reference voltage. This comparison process generates control codesthat may be used to enable/disable the various pull down and pull uptransistors associated with the programmable termination component 338and the output buffer 326 to adjust the impedances properly. Thisprocess generally operates to match the output buffer 326 impedance withthe external impedance that is represented by the external resistanceRZQ.

The arbitration circuit 346 arbitrates for control of the externalresistance RZQ that is shared among the memory devices of a ZQ group,for example, for a calibration operation. The arbitration circuit 346may apply an arbitration scheme to avoid contention for the externalresistance RZQ during impedance calibration.

The memory device 300 further includes a mode register 316. The moderegister 316 may include registers that may be programmed to storeinformation, such as binary digits (bits) of information. Theinformation of the mode register 316 may be written or read, forexample, through commands provided to the command decoder 310, such asby a system memory controller. Various memory device settings andoptions may be set through the use of the mode register 316. Bits of themode registers 316 may correspond to different settings and options. Thebits of the mode register 316 may be programmed through a mode registerwrite operation, which is performed when a mode register write commandis provided to the memory device 300, for example, from a memory systemcontroller. The mode register 316 may also provide information regardingthe status or settings of the memory device 300. The memory device 300may program a bit or bits of the mode register 316 that correspond to astatus or setting. The value of the bit(s) may indicate the status orsetting. The bits of the mode register 316 may be read through a moderegister read operation, which is performed when a mode register readcommand is provided to the memory device 300, for example, from a memorysystem controller. The memory device 300 provides the bits of the moderegister 316 that are read as output data that may be received by thememory system controller. Based on the value of the mode register bitsprovided by the memory device 300, the status and/or settings of thememory device 300 are provided to the memory system controller.

FIG. 4 is a diagram of a mode register 400 including various settingsand flags related to impedance calibration and impedance settingsaccording to an embodiment of the disclosure. The mode register 400 isan 8-bit register including bits corresponding to operands OP[7:0]. Thebits of the mode register 400 are designated as a particular setting orflag. For example, operand OP[0] is designated as ZQ Reset; operandOP[1] is designated as ZQ Stop; operands OP[4:2] are designated as ZQInterval; operand OP[5] is designated as ZQ ID mode; operand OP[6] isdesignated as ZQ Master; and operand OP[7] is designated as ZQ ID Flag.The operands OP[6:0] may be set, for example, through a mode registerwrite operation initiated by a system memory controller, and the operandOP[7] may be set by the memory device, for example, when the ZQ ID modeis set or when a ZQ ID request is received by the memory device.

The ZQ Reset of operand OP[0] has a default value of “0” to set a normalZQ operation when the impedances of the memory device are set accordingto a ZQ code determined during a ZQ calibration operation, or may be setto a “1” to reset the ZQ code to a default setting. The ZQ Stop ofoperand OP[1] has a default value of “0” to, set normal operation of ZQcalibration or may be set to a “1” to halt a ZQ calibration operation.The ZQ Interval of operands OP[4:2] may be set to a three-bit valuewhere the different values correspond to a ZQ calibration interval timefor the calibration operations. The ZQ ID Mode of operand OP[5] has adefault value of “0” to set normal ZQ operation or may be set to a “1”to set the identification mode ZQ ID Mode of operation. As will bedescribed in more detail below, the ZQ ID Mode of operation causes amemory device of a ZQ group to provide an identification ZQ ID requestto the other memory devices of the same ZQ group to set a respective ZQID Flag. As a result, all of the memory devices of a ZQ group set arespective identification flag ZQ ID Flag. The ZQ Master of operandOP[6] has a default value of “0” to indicate that the memory device isnot a ZQ Master, or may be set to “1” to designate the memory device asthe master of a ZQ group. The identification flag ZQ ID Flag of operandOP[7] has a default value of “0” for normal operation or may be set bythe memory device to “1” responsive to being set in the ZQ ID Mode orreceiving a ZQ ID request from another memory device in the same ZQgroup.

As will be described in more detail below, the ZQ ID Mode, ZQ Master,and ZQ ID Flag of operands OP[7:5] may be used to identify the ZQ groupsof a memory and identify the particular memory device(s) in each of theZQ groups, and to set a die of the ZQ group as the ZQ master. The moderegister 400 of FIG. 4 has been described as including particularsettings and flags related to the impedance calibration and settings,and in a particular arrangement. However, the impedance calibration andsettings and the arrangement of bits may be different in otherembodiments of the disclosure. The scope of the disclosure is notlimited to the particular details shown and described with reference toFIG. 4.

As previously described, a semiconductor device including multiplememory devices may have one or more ZQ terminals to which differentrespective groups of memory devices are coupled. Each ZQ terminal may becoupled to an external resistance RZQ that is shared by the multiplememory devices that are coupled to the ZQ terminal for impedancecalibration. The memory devices that are coupled to a common ZQ terminalto share an external resistance RZQ for impedance calibration may bereferred to as a ZQ group. Each ZQ group includes a memory device thatis designated as the ZQ master. The ZQ master of a ZQ group may receiveZQ calibration commands and communicate with the memory devices of theZQ group to perform ZQ calibration. Use of the shared externalresistance RZQ by the memory devices of the ZQ group for ZQ calibrationmay be arbitrated by the ZQ master. For example, in some embodiments ofthe disclosure the impedance controller of the ZQ master may communicatewith the other memory devices of the ZQ group over a communicationchannel (e.g., communication channel 242 of FIG. 2) to control the othermemory devices to sequentially perform ZQ calibration until all of thememory devices are calibrated, thereby avoiding contention for use ofthe external resistance RZQ. In other embodiments, the ZQ master maycontrol the memory devices of the ZQ group to perform ZQ calibration inanother manner in order to complete ZQ calibration without contentionfor use of the external resistance RZQ.

The ZQ master memory device of a ZQ group may be designated by a systemmemory controller coupled to the memory devices of the ZQ group. In someembodiments of the disclosure, a memory device of a ZQ group isdesignated as the ZQ master by programming bit(s) of a mode registerthat correspond to the ZQ master setting (e.g., with reference to FIG.4, setting ZQ Master of mode register 400 to “1”). For example, as adefault setting for the memory device, the mode register bit(s)corresponding to the ZQ master setting has a value to indicate that thememory device is not the ZQ master (e.g., have a default “0” value forthe mode register bit(s)). Thus, when the memory devices are initialized(e.g., power up, reset, etc.), none of the memory devices of a ZQ groupare designated as the ZQ master. The system memory controller may issue(e.g., transmit, send, etc.) a mode register write command to a selectedone of the memory devices of the ZQ group to program the mode registerbit(s) corresponding to the ZQ master setting to have a value indicatingthat it is the ZQ master (e.g., program the corresponding mode registerbit(s) to have a “1” value).

Once programmed, the selected memory device is designated as the ZQmaster and serves the role, for example, by receiving ZQ calibrationcommands for the ZQ group and communicating with the other memorydevices of the ZQ group accordingly to perform ZQ calibration.

As previously described, a semiconductor device may include multiplememory devices. One or more of the system memory controllers coupled tothe semiconductor device perform a die enumeration operation to identifythe memory devices of the semiconductor device. The system memorycontrollers perform die enumeration, for example, when the system memorycontroller and/or semiconductor device are initialized, such as at powerup and/or reset of the system memory controller and/or semiconductordevice. Following enumeration of the memory devices of the semiconductordevice, the system memory controller may store memory device informationrelated to the identification of the memory devices, for example, thenumber of memory devices in the semiconductor device, a uniqueidentification value for each of the memory devices, etc. The memorydevice information may be stored in a storage included in the systemmemory controller. In some embodiments, the memory device informationmay be stored in the format of a memory map. For example, the memory mapmay list all of the memory devices identified in the semiconductordevice along with any additional information that may be related foreach of the memory devices. Other formats for storing the memory deviceinformation, as well as the type of information stored, may be differentwithout departing from the scope of the disclosure.

While the system memory controller may obtain memory device informationabout the memory devices of the semiconductor device through a dieenumeration operation, for example, identifying the number of memorydevices, the arrangement of the memory devices into ZQ groups may not beapparent to a system memory controller. As such, the system memorycontroller may not be able to determine which memory devices todesignate as ZQ masters.

FIG. 5 is a flow diagram for identifying the ZQ groups and the memorydevices included in each of the ZQ groups of a semiconductor deviceaccording to an embodiment of the disclosure. A system memory controllermay follow the flow diagram to identify the ZQ groups and the memorydevices included in each of the ZQ groups, for example, as part of astartup and/or reset routine.

Prior to 510, the memory devices of the semiconductor device have beenenumerated so that a system memory controller has identified each memorydevice of the semiconductor device. However, the system memorycontroller has not identified the ZQ groups of the semiconductor deviceor the memory devices included in each of the ZQ groups.

At 510 the system memory controller sets an identification mode (e.g.,ZQ ID mode) for a target memory device of the semiconductor device. Insome embodiments of the disclosure, the ZQ ID mode may be set through amode register (e.g., setting ZQ ID Mode of operand OP[5] of moderegister 400 to “1”). The system memory controller may issue (e.g.,transmit, send, etc. signals representing) a mode register write commandto have a “1” written to the corresponding operand of the mode register.The target memory device may be any of the memory devices of thesemiconductor device. However, for the sake of efficiency, the targetmemory device may be a memory device of the semiconductor device thathas not yet been identified as being included in any ZQ group that hasbeen already identified to that point. Following the setting of the ZQID mode for the target memory device, the system memory controller mayperform other operations. The target memory device and the other memorydevices in the same ZQ group as the target memory device set arespective identification flag (e.g., ZQ ID Flag), as shown by 520. As aresult, all the memory devices of one ZQ group set their respective ZQID Flags. In some embodiments of the disclosure, the ZQ ID Flag of amemory device may be represented by bit(s) of a mode register. The ZQ IDFlag may be set by the memory device programming a value (e.g., “1”value) for mode register bit(s) corresponding to the ZQ ID Flag (e.g.,setting ZQ ID Flag of operand OP[7] of the mode register 400 to “1”).

At 530 the system memory controller checks the ZQ ID Flags of the memorydevices of the semiconductor device. Those memory devices having a setZQ ID Flag are identified as being included in a same ZQ group. Thesystem memory controller may update stored memory device information(e.g., a memory map) to record the memory devices included in theidentified ZQ group. In embodiments of the disclosure where the ZQ IDFlag is represented by a mode register bit(s), the system memorycontroller may check the ZQ ID Flags of the memory devices using a moderegister read operation. The system memory controller may issue a moderegister read command to each of the memory devices being checked (e.g.,transmit, send, etc. signals representing the mode register readcommand) to read the data of an opcode corresponding to the ZQ ID Flag.In response to the mode register read commands, the memory devicesprovide (e.g., transmit, send, etc.) the value of the ZQ ID Flag to thesystem memory controller. Those memory devices having a set ZQ ID Flag(e.g., provide a “1” for the corresponding mode register bit responsiveto the mode register read command) are identified as being included inthe same ZQ group. Those memory devices having a ZQ ID Flag that is notset (e.g., provide a “0” for the corresponding mode register bitresponsive to the mode register read command) are identified as notbeing included in that ZQ group.

At 540 the system memory controller determines whether all of the ZQgroups for the semiconductor device have been identified.

All of the ZQ groups of a semiconductor device have been identified whenall of the memory devices of the semiconductor device have beenidentified as being associated with a ZQ group, for example. If all ofthe ZQ groups of the semiconductor device have been identified, theprocess for identifying the ZQ groups of the semiconductor device iscomplete. However, if not all of the ZQ groups of the semiconductordevice have been identified, the system memory controller returns to 510to set the ZQ ID mode for another targeted memory device (e.g., a memorydevice that has not yet been identified as associated with a ZQ group)of the semiconductor device to repeat the flow diagram.

FIG. 6 is a flow diagram of determining whether all of the ZQ groups ofa semiconductor device have been identified according to an embodimentof the disclosure. As previously described, the system memory controllerdetermines the status of the ZQ ID Flags for the memory devices beingchecked. For example, in some embodiments of the disclosure, the ZQ IDFlag of the memory devices may be checked by issuing (e.g., transmits,sends, etc. signals representing) a mode register read command to thememory devices. As the system memory controller checks the ZQ ID Flagsof the memory devices, the system memory controller updates storedmemory device information that shows identified ZQ groups, and theparticular memory devices included in the identified ZQ groups. Aspreviously described, the memory device information may include thenumber of memory devices in the semiconductor device, a uniqueidentification value for each memory device, etc. As also previouslydescribed, the memory device information may be stored in a memory mapformat in some embodiments of the disclosure. Other techniques forstoring the memory device information may be used in other embodimentsof the disclosure.

At 610 the system memory controller accesses the stored memory deviceinformation to check for any memory devices that have not yet beenassociated with a ZQ group. At 620, the system memory controllerdetermines if the memory device information indicates that not all ofthe memory devices of the semiconductor device are associated with a ZQgroup, which indicates that there is at least one additional ZQ groupfor the remaining memory devices in the semiconductor device.Consequently, at 630 identification of the ZQ groups of thesemiconductor device continues (e.g., follow the flow diagram of FIG.5). Conversely, if the system memory controller determines that thememory device information identifies every memory device of thesemiconductor device as being associated with a ZQ group, at 640 all ofthe ZQ groups of the semiconductor device have been identified.

FIG. 7 is a flow diagram of a ZQ ID mode operation for a memory deviceaccording to an embodiment of the disclosure. The ZQ ID mode operationmay be performed by a memory device that has been targeted by systemmemory controller that is identifying ZQ groups of a semiconductordevice, for example, in response to a ZQ ID mode being set by the systemmemory controller.

At 710 a target memory device determines whether the ZQ ID mode has beenset. In some embodiments of the disclosure, the ZQ ID mode is set in amode register (e.g., setting ZQ ID mode of operand OP[5] of moderegister 400 to “1”), for example, by a system memory controller. Thesystem memory controller issues a mode register write command to thetarget memory device, and programs the bit(s) corresponding to the ZQ IDmode to set the mode. The target memory device determines the setting ofthe ZQ ID mode following the programming of the corresponding bit(s) inthe mode register by the system memory controller.

At 720 the target memory device enters the ZQ ID mode responsive todetermining that the ZQ ID mode is set, and at 730 provides (e.g.,transmits, sends, etc. signals representing) an identification request(e.g., ZQ ID request) to the other memory devices in the same ZQ group.The ZQ ID request may be provided to the other memory devices on acommunication channel to which all the memory devices of the ZQ groupare coupled (e.g., communication channel 242 of FIG. 2). A responseaccording to an embodiment of the disclosure by the other memory devicesin the same ZQ group as the target memory device will be described withreference to FIG. 8.

Along with providing the ZQ ID request to the other memory devices inthe same ZQ group, the target memory device sets its ZQ ID Flag at 740.In some embodiments of the disclosure, the ZQ ID Flag is represented bya bit(s) of a mode register (e.g., setting ZQ ID Flag of operand OP[7]of mode register 400 to “1”). The ZQ ID Flag is set by the target memorydevice by changing a value of the corresponding mode register bit(s) toa “set” value, for example, a “1” value. The value of the mode registerbit(s) representing the ZQ ID Flag may be read by the system memorycontroller issuing a mode register read command to the target memorydevice.

FIG. 8 is a flow diagram of a ZQ ID request operation for a memorydevice according to an embodiment of the disclosure. The ZQ ID requestoperation may be performed by a memory device that has received a ZQ IDrequest.

At 810 a memory device receives a ZQ ID request. The ZQ ID request maybe received on a communication channel (e.g., communication channel 242of FIG. 2). As previously described, memory devices of a ZQ group arecoupled to the communication channel. The ZQ ID request may have beenprovided, for example, by another memory device of the same ZQ groupthat had the ZQ ID mode set (e.g., a target memory device). At 820, thememory device that receives the ZQ ID request sets its ZQ ID Flag. Aspreviously described, in some embodiments of the disclosure, the ZQ IDFlag is represented by a bit(s) of a mode register, and the ZQ ID Flagmay be set by programming a value of the corresponding mode registerbit(s) to a “set” value, for example, a “1” value (e.g., setting ZQ IDFlag of operand OP[7] of mode register 400 to “1”).

Generally, following the setting of a ZQ ID mode of a target memorydevice by the system memory controller, the system memory controller canquery the ZQ ID Flags of the memory devices of the semiconductor deviceto identify which memory devices are in the same ZQ group as the targetmemory device. In particular, all of the memory devices having a set ZQID Flag (e.g., a “1” value for the corresponding mode register bit(s))are included in the same ZQ group as the target memory device.Conversely, all of the memory devices having a ZQ ID Flag that is notset (e.g., a “0” value for the corresponding mode register bit(s)) arenot included in the ZQ group of the target memory device. The systemmemory controller may update stored memory device information to recordthe memory devices included in the ZQ group. The system memorycontroller may check the ZQ ID Flag, for example, of all of the memorydevices of the semiconductor device. In another example, the systemmemory controller may check the ZQ ID Flag of the memory devices thathave not yet been associated with a ZQ group.

Following identification of the ZQ groups of a semiconductor device andidentification of the memory devices associated with each of the ZQgroups, a memory device of each ZQ group may be designated as the ZQmaster for the respective ZQ group, for example, by a system memorycontroller. As previously described, each ZQ group may have a memorydevice that is designated as the ZQ master. The ZQ master of a ZQ groupmay receive ZQ calibration commands and communicate with the memorydevices of the ZQ group to perform ZQ calibration, such as arbitratinguse of a shared external resistance RZQ among the memory devices of theZQ group for ZQ calibration.

In some embodiments of the disclosure, a memory device of a ZQ group maybe designated as a ZQ master by setting the corresponding bit(s) of amode register of the particular memory device. A mode register writecommand may be issued to the memory device to set the bit(s)corresponding to the ZQ Master setting. For example, with reference tothe mode register 400 of FIG. 4, the ZQ Master of OP[6] may be set to a“1” to designate the memory device as the ZQ master. A memory device ofeach of the ZQ groups of a semiconductor device may then be designatedas the ZQ master for the respective ZQ group.

Certain details are set forth above to provide a sufficientunderstanding of described embodiments. However, it will be clear to oneskilled in the art that embodiments may be practiced without theseparticular details. The description herein, in connection with theappended drawings, describes example configurations and does notrepresent all the examples that may be implemented or that are withinthe scope of the claims. The terms “exemplary” and “example” as may beused herein means “serving as an example, instance, or illustration,”and not “preferred” or “advantageous over other examples.” Additionally,terms such as “couples” and “coupled” mean that two components may bedirectly or indirectly electrically coupled. Indirectly coupled mayimply that two components are coupled through one or more intermediatecomponents. The detailed description includes specific details for thepurpose of providing an understanding of the described techniques. Thesetechniques, however, may be practiced without these specific details. Insome instances, well-known structures and devices are shown in blockdiagram form in order to avoid obscuring the concepts of the describedexamples.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes bothnon-transitory computer storage media and communication media includingany medium that facilitates transfer of a computer program from oneplace to another. A non-transitory storage medium may be any availablemedium that can be accessed by a general purpose or special purposecomputer. By way of example, and not limitation, non-transitorycomputer-readable media can comprise RAM, ROM, electrically erasableprogrammable read only memory (EEPROM), or optical disk storage,magnetic disk storage or other magnetic storage devices, or any othernon-transitory medium that can be used to carry or store desired programcode means in the form of instructions or data structures and that canbe accessed by a general-purpose or special-purpose computer, or ageneral-purpose or special-purpose processor.

Also, any connection is properly termed a computer-readable medium. Forexample, if the software is transmitted from a website, server, or otherremote source using a coaxial cable, fiber optic cable, twisted pair,digital subscriber line (DSL), or wireless technologies such asinfrared, radio, and microwave, then the coaxial cable, fiber opticcable, twisted pair, DSL, or wireless technologies such as infrared,radio, and microwave are included in the definition of medium.Combinations of the above are also included within the scope ofcomputer-readable media.

Other examples and implementations are within the scope of thedisclosure and appended claims. For example, due to the nature ofsoftware, functions described above can be implemented using softwareexecuted by a processor, hardware, firmware, hardwiring, or combinationsof any of these. Features implementing functions may also be physicallylocated at various positions, including being distributed such thatportions of functions are implemented at different physical locations.

Also, as used herein, including in the claims, “or” as used in a list ofitems (for example, a list of items prefaced by a phrase such as “atleast one of” or “one or more of”) indicates an inclusive list suchthat, for example, a list of at least one of A, B, or C means A or B orC or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein,the phrase “based on” shall not be construed as a reference to a closedset of conditions. For example, an exemplary step that is described as“based on condition A” may be based on both a condition A and acondition B without departing from the scope of the present disclosure.In other words, as used herein, the phrase “based on” shall be construedin the same manner as the phrase “based at least in part on.”

From the foregoing it will be appreciated that, although specificembodiments have been described herein for purposes of illustration,various modifications may be made while remaining with the scope of theclaimed technology. The description herein is provided to enable aperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the scope of thedisclosure. Thus, the disclosure is not limited to the examples anddesigns described herein, but is to be accorded the broadest scopeconsistent with the principles and novel features disclosed herein.

What is claimed is:
 1. A method, comprising: setting an impedanceidentification mode of a target memory device of a plurality of memorydevices; and checking respective identification flags of the pluralityof memory devices to determine which memory devices of the plurality ofmemory devices have set the respective identification flag responsive tosetting the identification mode of the target memory device of theplurality of memory devices.
 2. The method of claim 1, furthercomprising setting the identification mode of a second target memorydevice of the plurality of memory devices, wherein the second targetmemory device is a memory device of the plurality of memory devices nothaving a set identification flag responsive to setting theidentification mode of the target memory device.
 3. The method of claim2, further comprising setting the identification mode of a third targetmemory device of the plurality of memory devices, wherein the thirdtarget memory device is a memory device of the plurality of memorydevices not having a set identification flag responsive to setting theidentification mode of the target memory device and the second targetmemory device.
 4. The method of claim 2, further comprising storingmemory device information related to the memory devices having setidentification flags responsive to setting the identification mode ofthe target memory device of the plurality of memory devices and relatedto the memory devices of the plurality of memory devices having setidentification flags responsive to setting the identification mode ofthe second target memory device of the plurality of memory devices. 5.The method of claim 2 wherein a first group of memory devices includesthe memory devices of the plurality of memory devices having setidentification flags responsive to setting the identification mode ofthe target memory device of the plurality of memory devices and whereina second group of memory devices includes the memory devices of theplurality of memory devices having set identification flags responsiveto setting the identification mode of the second target memory device ofthe plurality of memory devices, the method further comprising:designating a memory device of the first group of memory devices as afirst master memory device; and designating a memory device of thesecond group of memory devices as a second master memory device.
 6. Amethod, comprising: transmitting a first signal indicative of anidentification mode of a target memory device of a plurality of memorydevices; receiving one or more second signals indicative of respectiveidentification flags from the plurality of memory devices; anddetermining, based at least in part on receiving the one or more secondsignals, which memory devices of the plurality of memory devices haveset the respective identification flag responsive to first signal andare included in an impedance group with the target memory.
 7. The methodof claim 6 wherein transmitting the first signal indicative of anidentification mode of a target memory device of the plurality of memorydevices comprises issuing a mode register write command to the targetmemory device to set a mode register operand corresponding to anidentification mode setting.
 8. The method of claim 6, furthercomprising issuing a mode register read command to the plurality ofmemory devices to cause the plurality of memory devices to transmit arespective mode register operand corresponding to the identificationflag.
 9. A method, comprising: providing an identification request to aplurality of memory devices over a communication channel to which theplurality of memory devices are coupled responsive to an identificationmode being set; setting an identification flag; and providing a statusof the identification flag responsive to receiving an identificationrequest.
 10. The method of claim 9, further comprising determiningwhether the identification mode is set.
 11. The method of claim 10wherein determining whether the identification mode is set comprisesdetermining a value of an operand of a mode register corresponding tothe identification mode.
 12. The method of claim 9 wherein providing anidentification request to a plurality of memory devices comprisesproviding the identification request on a communication channel coupledto each of the plurality of memory devices.
 13. The method of claim 9wherein the memory devices are coupled to a shared impedance terminal.14. A method, comprising: receiving an identification request on acommunication channel coupled to a plurality of memory devices, theplurality of memory devices coupled to a common impedance terminal;setting an identification flag responsive to the identification request;and providing a status of the identification flag responsive toreceiving an identification request.
 15. The method of claim 14 whereinsetting the identification flag comprises setting an operand of a moderegister corresponding to an identification flag.
 16. The method ofclaim 15 wherein providing the status of the identification flagresponsive to receiving an identification request comprises outputtingthe value of the operand of the mode register responsive to receivingthe identification request.
 17. The method of claim 14 wherein providingthe status of the flag responsive to receiving an identification requestcomprises performing a mode register read operation to a mode registerincluding an operand corresponding to the identification flag.